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The Circulatory System

  • Arteries have thick walls and carry blood away from the heart. Veins carry blood towards the heart, have thinner walls and have valves to prevent backflow.
  • Capillaries are small vessels with very thin walls across which nutrients, hormones, gases and waste products can diffuse.
  • Blood contains fluid called plasma, as well as red blood cells and white blood cells. Red blood cells (erythrocytes) contain hemoglobin and transport oxygen. White blood cells (leukocytes) function in immunity. Platelets are cell fragments that play a role in clotting.
  • Red blood cells contain hemoglobin, a four subunit protein that binds cooperatively to oxygen.
  • The mammalian heart has four chambers. The right atrium and ventricle pump blood through the pulmonary circuit and the left atrium and ventricle pump blood through the systemic circuit.
  • The sinoatrial node (SA) node is the pacemaker for the heart.
  • Deoxygenated blood leaves organs and returns to the heart via the superior vena cava and the inferior vena cava. Blood drains into the right atrium and then enters the right the right ventricle. Blood is pumped through the pulmonary arteries into the lungs and the newly oxygenated blood returns to the heart via the pulmonary veins, draining into the left atrium and then the left ventricle. The left ventricle pumps blood through the aorta to tissues and organs.

The Circulatory System

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

AP Biology Intro